Look closely at the picture to your left. Aside from the fact the height level of beer in these glasses is slightly different, one of these things is not like the other. They are all filled with the same beer, Stella Artois, but can you tell what's wrong? Before you start emailing me hate mail, or beating yourself brainless, the reality is there is nothing you can physically see that is different. There is though a distinct difference I experienced with these beers after I took this picture. One of these beers, is perfectly fine, the other two have been ruined by a very common problem. The problem is, two of these beers are "skunked". (Just for the record the first beer on the left is the one that is fine :) ).
So what does this mean?
The term "skunked" beer or "skunky", is a product of having beer exposed to blue light, that will break down the hop compounds (isohumulones), and produce a very undesirable aroma/flavor, that basically smells like a skunk (sometimes going by a more scientific name as 'methyl', or 'isopentyl mercaptan'). [Randy Mosher, Pg. 61 "Tasting Beer"]. Sunlight is a good source, but this will also happen in one of the most common beer purchasing environments, and that is the cooler-lit cases of a beer store isle.
Beer as we know comes in a variety of formats, bottles and cans being the most common. As we all know cans are metal, and we can't see through them and neither can light. Having beer on tap, comes from a keg, basically filled from the brewery at time made and then shipped to somewhere for consumption. This no doubt prevents the beer from the chance of being skunked. I will say though, I have been in many a drinking establishment where some idiot at a bar is drinking his "craft" beer, doesn't like it or it's unappealing, or perhaps it might rarely be off in some other way, but he will actually thinks it is skunked and says so. Believe me I've seen it with my own eyes, as the bartender (who can often be the proprietor) will just roll his eyes usually and bite his tongue, and pour the schmuck something else.
This leaves then the other common delivery of beer that we all know as the glass bottle.
Skunking can happened to bottled beer not even opened because bottles are essentially clear. I mean you can see through them when you look at them right? Of course. Beer bottles in the US are mostly brown, this prevents "some" skunking but not entirely. The biggest culprit of skunking happens in either green or clear bottles. These bottles offer NO protection whatsoever.
I have always wanted to test this theory out and set out to do so. The perfect candidate seemed to crop up and I chose it because it is often stored in a green bottle, and it just recently started showing up in cans. That beer is Stella Artois, a basic European Pale Lager.
I grabbed a few cans, and a six pack at a store and proceeded set up my test. The bottled six pack I have to admit was "sort of" sitting in a refrigerated section for awhile, in of course a typical store. It would be pretty much impossible to buy a six pack of Stella that had been lying around in darkness, because that isn't how they are displayed of course. This is also why this problem is so common among beer on the shelf in green and clear bottles.
I decided I would try three Stella Artois beers in three different ways. One was from the can. The second would be from one of the glass bottles I bought from the six pack that I had stored away in my basement and wrapped up so that no light could get to it. The third bottle would be a bottle I would take from this pack, and place outside in direct sunlight for 15 - 20 minutes. All beers would then be chilled in my fridge to be tasted together for consumption and reviewing.
I did this, and the results were really amazing. This is science and it doesn't lie. It was also real fun to do. You can do this with any green or clear color bottled beer and I suggest you also try this experiment at home. It will really open your eyes to imbibing beer. To see how this turned out, watch the video below. Cheers!